Conserved expression pattern of chicken DAZL in primordial germ cells and germ-line cells

The autosomal gene deleted in azoospermia-like (DAZL), which was identified as a member of the deleted in azoospermia (DAZ) family, is homologous to the Drosophila gene BOULE. The authors investigated the sequence similarities of chicken DAZL (cDAZL) with several invertebrate and vertebrate DAZL proteins using CLUSTAL X. A comparison of the primary sequence of cDAZL with other DAZL proteins indicated significant similarities: 70-82% with reptiles, 63-68% with mammals, 51-67% with amphibians, and 42-49% with fishes. The conserved expression pattern of cDAZL was examined by reverse transcription-PCR, quantitative real-time PCR, and in situ hybridization during primordial germ cell (PGC) settlement in the gonads and germ-line development. Among several tissues examined on embryonic day E6.5, DAZL expression was detected specifically in male and female gonads. Quantitative real-time PCR and in situ hybridization revealed strong cDAZL expression in PGCs. When the PGCs differentiated into germ cells, cDAZL expression was slightly decreased; however, expression was continuously detected in germ-line cells until the adult stage. We inferred that cDAZL expression was conserved in PGCs and during germ-line differentiation until the adult stage, making them a valuable molecular marker for studies of PGC differentiation and germ-line development in chickens.